A simple and fast approach for allocation and size evaluation of distributed generation

Kayal and Chanda International Journal of Energy and Environmental Engineering 2013, 4:7 http://www.journal-ijeee.com/content/4/1/7 ORIGINAL RESEARCH Open Access A simple and fast approach for allocation and size evaluation of distributed generation Partha Kayal* and Chandan Kumar Chanda Abstract Penetration of distributed generation (DG) units in distribution network has increased rapidly stimulated by reduced network power loss, improved bus voltage profile, and better power quality. Appropriate size and allocation of DG units play a significant role to get beneficial effects. The objective of this study is to demonstrate a simple and fast technique to determine appropriate location and size of DG units. A voltage stability indicator (VSI) is derived which can quantify the voltage stability conditions of buses in distribution network. According to VSI, vulnerable buses of the network are arranged rank-wise to form a priority list for allocation of DG units. To determine the size of DG units, a feed forward artificial neural network is prepared in MATLAB environment (The MathWorks, Inc., Massachusetts, USA). The effectiveness of the proposed methodology has been tested on a 52-bus radial distribution network. After appropriate allocation of DG units, voltage profiles of most of the buses are increased significantly. The results also indicated that the total loss of the distribution network has reduced by nearly 76.39%, and voltage stability conditions of buses are improved considerably. Voltage stability conditions of bus-13, bus-36, and bus-44 are raised by 23.16%, 29.23%, and 37.64% respectively. Keywords: Voltage stability condition, Distributed generation units, Priority list, Allocation, ANN Background Distributed generation (DG) is going to play a very important role in power systems worldwide. Penetration of DG units in distributed system presents a significant impact on system reliability, power flow, voltage profile, stability, and power quality. Renewable energy source-based DG can alleviate the energy poverty by utilizing abundant wind and solar photovoltaic available in the region [1]. Most of the radial distribution networks suffer with voltage instability at feeders. DG units can boost up the low voltage at the end of the feeders. The planned application of DG units can provide the transmission capacity release, reduction in network losses, and avoidance of high investment costs for network upgrades. But, unplanned uses of DG units may increase the problems. Therefore, some tools or techniques are needed to be examined for the allocation and sizing of the DG units. A method for placement of DG units using continuation power flow analysis has been proposed by Hedayati et al. [2]. They have not studied about the size of DG * Correspondence: Department of Electrical Engineering, Bengal Engineering & Science University, Shibpur, Howrah 711103, India units. Kashem et al. have discussed about optimal use of DG units to support voltage in distribution feeders [3]. They have applied sensitivity analysis to determine appropriate location of voltage support DG units. The effect of DG real and reactive power injections for the inclusion of DG units is also investigated. Rafidah et al. [4] have discussed about a methodology to evaluate appropriate DG size and its impact on power losses and voltage profile in distribution system. They have proposed complex artificial immune system optimization algorithm for sizing of DG units. Islam has presented a methodology to optimize the size of pumped hydrostorage system using optimization software HOMER (NREL, Washington DC, USA) [5]. Acharya et al. [6] have derived an expression to calculate size and location of DG units to minimize distribution losses. The size of DG units is calculated updating the loss coefficients of network loss formula. With proposed methodology by Acharya et al., appropriate size of DG units can be estimated after running a number of load flow iterations. A genetic algorithm-based optimal sizing and placement of DG units considering the system energy loss minimization in different load conditions have been © 2013 Kayal and Chanda; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Kayal and Chanda International Journal of Energy and Environmental Engineering 2013, 4:7 http://www.journal-ijeee.com/content/4/1/7 Page 2 of 9 Figure 1 Two-bus power system network. presented by Singh et al. [7]. However, this method needs extensive calculations. Analytical approaches to choose optimal location for DG units in radial distribution network to minimize loss have been presented by Caisheng et al. [8]. They have not discussed sizing issue of DG units in the literature. Recent researches focus on the selection of best places for the allocation of DG units in large distribution network, but appropriate size calculation of DG units using simple and fast techniques has not been emphasized yet. The paper is organized as follows: At first, a voltage stability indicator (VSI) is developed from conventional power flow equation to determine the stability condition of buses. Then, a priority list is set up using VSI to allocate DG units. In the next section, artificial neural network (ANN) technique is used to determine the proper size of the DG units to ensure the permissible static voltage of each bus. After that, a proposed methodology is tested on a 52-bus radial distribution network, and the impact of the DG units on static voltage profile is illustrated. In the last section, some relevant conclusions are given. Methods Calculate VSI of buses and form priority table Place DG unit at a bus according to priority list Change S DG (MVA) of that bus and run load flow solution program Calculate voltage magnitude corresponding to S DG and store Train ANN Allocation of DG units In developing countries, most of the distribution networks are operated with radial structure, leading to Get output of appropriate DG size for voltage magnitude of 0.95 p.u at DG allocated bus from ANN Check voltage of all buses>=0.9 p.u No Yes Stop iteration and show DG allocated bus and size of DG units Figure 2 Architecture of the three-layered feed forward ANN. Figure 3 Flow chart for allocation and sizing of DG units. Kayal and Chanda International Journal of Energy and Environmental Engineering 2013, 4:7 http://www.journal-ijeee.com/content/4/1/7 larger voltage drop. Inefficient utilization of energy is another reason to get low quality power at customer end [9]. Considering the fact that most DG units are located at the distribution level, determination of the best locations for DG units to maximize their benefits is very important in system design and expansion. By analyzing the (...truncated)